The use of shipping or transportation containers is well known for the transport of products and commodities over long distances. To extend or otherwise preserve the shelf life of such transportable products the shipping containers are normally equipped with some form of temperature regulation system, such as a refrigeration system.
Instances in which the products to be transported are perishable goods, such as fruit and/or vegetables, transport containers may also incorporate a system adapted to modify the composition of the refrigerated air surrounding the stored contents. As fresh fruit and vegetables represent active biological systems the atmosphere of a container will constantly change as gases and moisture are produced by the metabolic processes (such as respiration) occurring within the biological systems present. Furthermore, the shelf life of a lot of shipped produce is highly dependent on the composition of gases within a container where the optimal gaseous composition of a storage container is highly dependent on the specific produce being stored.
By incorporating an atmospheric modification or control system into a transport container the respiration rates of the stored produce and the gases present within a container may be regulated, thereby providing an effective means for prolonging the shelf life of the container contents in addition to the refrigeration of the air. In particular, the respiration rates of stored produce may be retarded by controlling the mix and/or volumes of oxygen, carbon dioxide and nitrogen within the container.
Furthermore, a container may provide an environment suitable for the growth of spoilage microorganisms and the proliferation of insects and other pests. To counter such activity systems normally rely on the use of chemicals to eliminate pathogen and insect damage to stored produce. The use of atmosphere control systems adapted to control respiration may also inhibit pathogen production and kill insects, and therefore contribute to a reduction in the number and quantity of chemicals, being applied to reduce or eliminate such damage to stored produce. For example, trials have demonstrated that the greatest impact on insect proliferation within a container may be achieved by maintaining reduced levels of oxygen for extended periods of time, which leads to oxygen deprivation in insect body tissue.
A common approach used in shipping containers to increase the shelf life of produce stored is to create an “ideal” or optimum storage atmosphere (that is different from that of ambient air) at the beginning of the storage period and maintaining that atmosphere. In some cases containers are initially flushed to remove or add gases resulting in an internal gas composition around the stored produce that is different from that of ambient air. Once the oxygen content of the gases within a container drops further as a result of respiration, inlets may be opened to allow fresh air into the container, thereby delivering oxygen into the container. Such systems often rely on the use of membranes or films which are adapted to prevent the movement of gases into or out of the container, and such systems are commonly referred to as Modified Atmosphere (MA) systems.
However, by ventilating the container with fresh air and letting out the container air, the composition of the gas in the container will over time eventually result in a gas composition in which the carbon dioxide and oxygen content (as a sum proportion of container gases) approaches approximately 21%. Such a proportion of carbon dioxide and oxygen is not necessarily an optimal environment for the storage of certain products. If the container is not initially flushed, the sum of oxygen and carbon dioxide will always remain approximately 21%.
Although such systems may be relatively inexpensive to integrate into a container they are not Well suited to adequately controlling and maintaining optimum levels of carbon dioxide within a container, where such optimum levels often differ from those levels of carbon dioxide present in ambient air.
Moreover, the sum proportion of carbon dioxide and oxygen in a container will always remain approximately 21% unless the composition of either the outgoing and/or ingoing air is actively and effectively manipulated to thereby change this sum proportion (of 21%) as necessary. Other methods, for example the use of carbon dioxide absorbent lime, can be used to actively and selectively remove gases from the cargo space of a container. However, such methods have disadvantages including the disposal of used lime and ineffective control.
An alternative approach is to provide a container having concentrations of oxygen and/or carbon dioxide that are different from that of ambient air and regularly measuring and actively maintaining those concentrations during a storage period. In particular, such systems will typically maintain low levels of oxygen and higher levels of carbon dioxide (compared to ambient air) so that the levels of respiration occurring within stored produce may be controlled. To effectively gauge the concentrations and/or volumes of oxygen and other gases within a container such a system may often utilize sensor technology which is located within a container and is adapted to actively assess the gaseous composition inside a container. These systems are commonly referred to as Controlled Atmosphere (CA) systems.
Such Controlled Atmosphere (CA) systems arc adapted to ensure that the appropriate remedial action is taken to ensure that the gaseous composition of a container is maintained, or returned to an optimal level when deviation occurs. To ensure optimal levels of gases are maintained (usually this involves reduced oxygen levels and increased carbon dioxide levels) many Controlled Atmosphere (CA) systems are provided with a filter adapted to compress and separate the components of incoming air. In this way, as air is directed into a container excess oxygen may be prevented from entering the container, which is desirable as it will ensure the retardation of respiratory activity within the container.
Use of Controlled Atmosphere (CA) systems will enable a container to maintain the optimal gas composition specifically suited to the produce and/or goods contained within where such a gas composition may be actively controlled throughout the period of storage.
Whilst such a system may effectively control and maintain optimal conditions that will contribute to longevity of stored produce such systems are extremely expensive to manufacture and maintain. Moreover, these systems tend to be very complicated and typically demand the services of a skilled and specialized work force to ensure they are adequately maintained.
The provision of an improved control system which can actively monitor the composition of gases in a container and provide an optimal environment for the storage of container contents would be of advantage.
The provision of a system able to effectively control the flow of gases into and/or out of a container to thereby promote a gaseous atmosphere in a container which will prolong the shelf life of stored produce would be of advantage. The provision of such a system which is both relatively inexpensive to produce and maintain would be advantage.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
It is an object of the present invention to address at least some of the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.